The invention relates to a weft thread inserting nozzle, comprising a hollow needle, having a closed tip at one end and the other end of which is adapted to be connected to a source of pressurized fluid, an outlet opening being provided in the side wall adjacent the tip.
Nozzles of this type are used in shuttleless looms and are located serially from one end of the weaving shed to the other so as to produce a consecutively a plurality of fluid jets, each of which is operative in a predetermined range of the weft inserting trajectory and "carries" the weft thread through the weaving shed.
Because of the needle-shape of said nozzles they may readily pass between the warp threads into and out of the weaving shed. Usually the nozzles project their jets into a guide tunnel formed within the weaving shed by the generally U-shaped blades of the reed or by a separate comb-like member which is periodically moved into and out of the weaving shed along with the nozzles.
A measure for the speed at which a weft thread may thus be transported through the weaving shed is constituted by the jet speed. A further determining factor is the direction of the fluid jets issuing from the individual nozzles. There is a certain direction of the fluid jets, at which the transmission of the kinetic energy from the jet to the thread to be inserted is optimal. When the direction of a jet deviates from said optimum direction the transmission of the kinetic energy from the jet to the thread becomes less effective, as a result of which stagnation (i.e. weaving defects) may occur. The rate of flow of fluid and thereby the speed of the carrying fluid in the tunnel may in principle be increased by increasing the fluid pressure and the cross-section of the outlet opening of the nozzle. An increase of the cross-section of the outlet opening, however, entails more uncertainty with respect to the correctness of the direction of the fluid jet. Further the direction of the issuing jet strongly depends on the pressure so that with variations in pressure the jet direction will vary as well.